1. Field of the Invention
This invention relates to modified textile fibers.
2. Description of the Prior Art
The concept of preparing a temperature-adaptable hollow textile fiber has been previously demonstrated and described in U.S. Pat. No. 3,607,591. This invention incorporates a gas into liquid inside the fiber that increases the diameter of the fiber and thus increases its thermal insulation value when the liquid solidifies and the solubility of the gas decreases. However, this invention exhibits serious limitations. It is limited to use with only hollow textile fibers and is only applicable in cold weather situations, i.e., when the environmental temperature drops below the freezing point of the liquid in the fiber. Furthermore, this modified hollow fiber system was not evaluated for its ability to reproduce its thermal effect after various heating and cooling cycles.
The aerospace industry has reported some phase-change materials (inorganic salt hydrates such as calcium chloride hexahydrate, lithium nitrate trihydrate, zinc nitrate, hexahydrate, and polyethylene glycol with an average molecular weight of 600) for uses in spacecraft (Hale, et al., "Phase Change Materials Handbook", NASA Contractor Report CR-61363, September 1971). These materials have also been used in solar collectors and heat pumps in residences (Carlsson, et al., Document D12:1978, Swedish Council for Building Research). However, in these and similar publications, the suitability of phase-change materials for effective and prolonged heat storage and release is influenced by the substrate in which they are stored, its geometry and thickness, the effect of impurities and the tendency of the phase-change materials to supercool and exhibit reversible melting and crystallization. Moreover, and perhaps the most significant deficiency and limitation of the above recommendations, is the fact that the phase-change materials were recommended as incorporated into metal containers, plastic pipes and other nonporous substrates or very thick insulation such as wall board. No process or suitable conditions for the incorporation of these types of materials into hollow or non-hollow textile fibers has been described. Therefore, the problem of choosing a textile fiber and combining it with a phase-change material in order ot produce thermal storage and release properties that could be retained for a minimum of 5 heating and cooling cycles is an extremely difficult one.
In addition to substances that store or release thermal energy due to melting and/or crystallization (phase-change materials) there is another class of substances that are characterized by their high enthalpies or thermal storage and release properties. These substances are commonly called plastic crystals, and have extremely high thermal storage or release values that occur prior to and without melting, i.e., they have thermal energy available without undergoing a change of state such as solid to liquid (melting) or liquid to solid (crystallization). Although the precise reasons why plastic crystals exhibit such unique thermal behavior prior to a change of state have not been verified, this thermal effect is believed to be due to a conformational and/or rotational disorder in these substances. Plastic crystal materials such as pentaerythritol and other polyhydric alcohols have been recommended for use in passive architectural solar designs and active solar dehumidifier or solar cooling systems (D. K. Benson, et al., proc. Eleventh No. Am. Thermal Analysis Conf. 1981) because of their high thermal storage and release values that occur much below their melting point. However, as with the phase-change materials, no process or suitable conditions for the incorporation of these plastic crystals into hollow or non-hollow textile fibers has been described.